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<h2 class="title">
<a id="regexp-syntax"></a>Regular expression syntax<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/docs/reference/query-dsl/regexp-syntax.asciidoc">edit</a>
</h2>
</div></div></div>
<p>A <a href="https://en.wikipedia.org/wiki/Regular_expression" class="ulink" target="_top">regular expression</a> is a way to
match patterns in data using placeholder characters, called operators.</p>
<p>Elasticsearch supports regular expressions in the following queries:</p>
<div class="ulist itemizedlist">
<ul class="itemizedlist">
<li class="listitem">
<a class="xref" href="query-dsl-regexp-query.html" title="Regexp query"><code class="literal">regexp</code></a>
</li>
<li class="listitem">
<a class="xref" href="query-dsl-query-string-query.html" title="Query string query"><code class="literal">query_string</code></a>
</li>
</ul>
</div>
<p>Elasticsearch uses <a href="https://lucene.apache.org/core/" class="ulink" target="_top">Apache Lucene</a>'s regular expression
engine to parse these queries.</p>
<h3>
<a id="regexp-reserved-characters"></a>Reserved characters<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/docs/reference/query-dsl/regexp-syntax.asciidoc">edit</a>
</h3>
<p>Lucene’s regular expression engine supports all Unicode characters. However, the
following characters are reserved as operators:</p>
<pre class="literallayout">. ? + * | { } [ ] ( ) " \</pre>

<p>Depending on the <a class="xref" href="regexp-syntax.html#regexp-optional-operators" title="Optional operators">optional operators</a> enabled, the
following characters may also be reserved:</p>
<pre class="literallayout"># @ &amp; &lt; &gt;  ~</pre>

<p>To use one of these characters literally, escape it with a preceding
backslash or surround it with double quotes. For example:</p>
<pre class="literallayout">\@                  # renders as a literal '@'
\\                  # renders as a literal '\'
"john@smith.com"    # renders as 'john@smith.com'</pre>

<h3>
<a id="regexp-standard-operators"></a>Standard operators<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/docs/reference/query-dsl/regexp-syntax.asciidoc">edit</a>
</h3>
<p>Lucene’s regular expression engine does not use the
<a href="https://en.wikipedia.org/wiki/Perl_Compatible_Regular_Expressions" class="ulink" target="_top">Perl
Compatible Regular Expressions (PCRE)</a> library, but it does support the
following standard operators.</p>
<div class="variablelist">
<dl class="variablelist">
<dt>
<span class="term">
<code class="literal">.</code>
</span>
</dt>
<dd>
<p>Matches any character. For example:</p>
<pre class="literallayout">ab.     # matches 'aba', 'abb', 'abz', etc.</pre>

</dd>
<dt>
<span class="term">
<code class="literal">?</code>
</span>
</dt>
<dd>
<p>Repeat the preceding character zero or one times. Often used to make the
preceding character optional. For example:</p>
<pre class="literallayout">abc?     # matches 'ab' and 'abc'</pre>

</dd>
<dt>
<span class="term">
<code class="literal">+</code>
</span>
</dt>
<dd>
<p>Repeat the preceding character one or more times. For example:</p>
<pre class="literallayout">ab+     # matches 'ab', 'abb', 'abbb', etc.</pre>

</dd>
<dt>
<span class="term">
<code class="literal">*</code>
</span>
</dt>
<dd>
<p>Repeat the preceding character zero or more times. For example:</p>
<pre class="literallayout">ab*     # matches 'a', 'ab', 'abb', 'abbb', etc.</pre>

</dd>
<dt>
<span class="term">
<code class="literal">{}</code>
</span>
</dt>
<dd>
<p>Minimum and maximum number of times the preceding character can repeat. For
example:</p>
<pre class="literallayout">a{2}    # matches 'aa'
a{2,4}  # matches 'aa', 'aaa', and 'aaaa'
a{2,}   # matches 'a` repeated two or more times</pre>

</dd>
<dt>
<span class="term">
<code class="literal">|</code>
</span>
</dt>
<dd>
<p>OR operator. The match will succeed if the longest pattern on either the left
side OR the right side matches. For example:</p>
<pre class="literallayout">abc|xyz  # matches 'abc' and 'xyz'</pre>

</dd>
<dt>
<span class="term">
<code class="literal">( … )</code>
</span>
</dt>
<dd>
<p>Forms a group. You can use a group to treat part of the expression as a single
character. For example:</p>
<pre class="literallayout">abc(def)?  # matches 'abc' and 'abcdef' but not 'abcd'</pre>

</dd>
<dt>
<span class="term">
<code class="literal">[ … ]</code>
</span>
</dt>
<dd>
<p>Match one of the characters in the brackets. For example:</p>
<pre class="literallayout">[abc]   # matches 'a', 'b', 'c'</pre>

<p>Inside the brackets, <code class="literal">-</code> indicates a range unless <code class="literal">-</code> is the first character or
escaped. For example:</p>
<pre class="literallayout">[a-c]   # matches 'a', 'b', or 'c'
[-abc]  # '-' is first character. Matches '-', 'a', 'b', or 'c'
[abc\-] # Escapes '-'. Matches 'a', 'b', 'c', or '-'</pre>

<p>A <code class="literal">^</code> before a character in the brackets negates the character or range. For
example:</p>
<pre class="literallayout">[^abc]      # matches any character except 'a', 'b', or 'c'
[^a-c]      # matches any character except 'a', 'b', or 'c'
[^-abc]     # matches any character except '-', 'a', 'b', or 'c'
[^abc\-]    # matches any character except 'a', 'b', 'c', or '-'</pre>

</dd>
</dl>
</div>
<h3>
<a id="regexp-optional-operators"></a>Optional operators<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/docs/reference/query-dsl/regexp-syntax.asciidoc">edit</a>
</h3>
<p>You can use the <code class="literal">flags</code> parameter to enable more optional operators for
Lucene’s regular expression engine.</p>
<p>To enable multiple operators, use a <code class="literal">|</code> separator. For example, a <code class="literal">flags</code> value
of <code class="literal">COMPLEMENT|INTERVAL</code> enables the <code class="literal">COMPLEMENT</code> and <code class="literal">INTERVAL</code> operators.</p>
<h4>
<a id="_valid_values"></a>Valid values<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/docs/reference/query-dsl/regexp-syntax.asciidoc">edit</a>
</h4>
<div class="variablelist">
<dl class="variablelist">
<dt>
<span class="term">
<code class="literal">ALL</code> (Default)
</span>
</dt>
<dd>
Enables all optional operators.
</dd>
<dt>
<span class="term">
<code class="literal">COMPLEMENT</code>
</span>
</dt>
<dd>
<p>Enables the <code class="literal">~</code> operator. You can use <code class="literal">~</code> to negate the shortest following
pattern. For example:</p>
<pre class="literallayout">a~bc   # matches 'adc' and 'aec' but not 'abc'</pre>

</dd>
<dt>
<span class="term">
<code class="literal">INTERVAL</code>
</span>
</dt>
<dd>
<p>Enables the <code class="literal">&lt;&gt;</code> operators. You can use <code class="literal">&lt;&gt;</code> to match a numeric range. For
example:</p>
<pre class="literallayout">foo&lt;1-100&gt;      # matches 'foo1', 'foo2' ... 'foo99', 'foo100'
foo&lt;01-100&gt;     # matches 'foo01', 'foo02' ... 'foo99', 'foo100'</pre>

</dd>
<dt>
<span class="term">
<code class="literal">INTERSECTION</code>
</span>
</dt>
<dd>
<p>Enables the <code class="literal">&amp;</code> operator, which acts as an AND operator. The match will succeed
if patterns on both the left side AND the right side matches. For example:</p>
<pre class="literallayout">aaa.+&amp;.+bbb  # matches 'aaabbb'</pre>

</dd>
<dt>
<span class="term">
<code class="literal">ANYSTRING</code>
</span>
</dt>
<dd>
<p>Enables the <code class="literal">@</code> operator. You can use <code class="literal">@</code> to match any entire
string.</p>
<p>You can combine the <code class="literal">@</code> operator with <code class="literal">&amp;</code> and <code class="literal">~</code> operators to create an
"everything except" logic. For example:</p>
<pre class="literallayout">@&amp;~(abc.+)  # matches everything except terms beginning with 'abc'</pre>

</dd>
</dl>
</div>
<h3>
<a id="regexp-unsupported-operators"></a>Unsupported operators<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/docs/reference/query-dsl/regexp-syntax.asciidoc">edit</a>
</h3>
<p>Lucene’s regular expression engine does not support anchor operators, such as
<code class="literal">^</code> (beginning of line) or <code class="literal">$</code> (end of line). To match a term, the regular
expression must match the entire string.</p>
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